Declare new command to denote the condition with additional settings

Question

Can someone tell me how to set the parameters of a declared new command similar to how it is set in the TikZ package? More specifically, I would like to declare a function \condVert{} that sets a vertical line to the right of the selected expression (environment \left. + \right|) indicating a condition (or the limits of a variable change). Also, as an additional parameter, I would like to set the ability to set brackets / frames around the expression.

Examples:

Command	Result	Comment
\condVert[lim={x=0 | a}]{f(x)}
\condVert[limits={x=0 | a}]{f(x)}		lim and limits in the settings should give the same result.
\condVert[lim={x=a}, angle bracs]{\dfrac{x^2}{2} + x}		I would also like to be able to use syntax like [...brackets=angle].
\condVert[lim={x=a}, rangle bracs]{\dfrac{x^2}{2} + x}
\condVert[lim={x=a}, {dash box}]{\dfrac{x^2}{2} + x}
\condVert[lim={x=a}, {dash circle box}]{\dfrac{x^2}{2} + x}

Highlighting the background color would probably be too expressive, but perhaps it would be good to add to the functionality. :)

Answer 1

Here is a solution via my own, slightly non-standard package, SemanTeX. I took the liberty to change the order and meaning of some arguments and keys in a way that made the implementation easier:

\documentclass{article}
\usepackage{semantex}
\NewVariableClass\condVert[
    define keys[2]={
        {limits}{
            Other spar={.}{|}{auto},
            lower={#1},
            upper={#2},
        },
    },
    define keys[1]={
        {lim}{ limits={#1}{} },
    },
    define keys={
        {angle bracs}{
            Other spar={(}{)}{auto},
        },
        {rangle bracs}{
            Other spar={[}{]}{auto},
        },
        {dash box}{
            command=\dashboxcommand,
        },
        {dash circle box}{
            command=\dashcircleboxcommand,
        },
    },
]
\newcommand\dashboxcommand[1]{%
    #1% change to suit your needs
}
\newcommand\dashcircleboxcommand[1]{%
    #1% change to suit your needs
}
\begin{document}
\begin{gather}
    \condVert{f(x)}[lim={x=0}]
\
    \condVert{f(x)}[limits={x=0}{a}]
\
    \condVert{\dfrac{x^2}{2} + x}[angle bracs,lim={x=a}]
\
    \condVert{\dfrac{x^2}{2} + x}[rangle bracs,lim={x=a}]
\
    \condVert{\dfrac{x^2}{2} + x}[dash box, lim={x=a}]
\
    \condVert{\dfrac{x^2}{2} + x}[dash circle box, lim={x=a}]
\end{gather}
\end{document}